Conventional Fabry-Perot filters employ two windows with a high reflective coating on adjacent faces which are separated by a distance on the order of the light wavelength. Such filters transmit at a maximum wavelength of twice the spacer thickness. At other wavelengths, the device blocks the transmission of light. These devices also operate over a limited wavelength range.
U.S. Pat. No. 3,660,777 discloses apparatus for a Q switching carbon dioxide laser operating on the scanning Fabry-Perot principle to effect a laser switching device. The device uses mechanical shock to change the transmission of the Fabry-Perot inferometer.
U.S. Pat. No. 3,471,800 discloses a multiple Fabry-Perot etalon using several reflective surfaces, where two solid layers have a first refractive index and a gaseous layer of lower refractive index seperates them.
U.S. Pat. No. 3,834,795 discloses a Fabry-Perot filter which is used as a visual shutter. Again a single reflective layer or mirror coating is placed on each substrate in the Fabry-Perot cavity.